Electromagnetic controls



Sept. 4, 1956 R. L. JAESCHKE 2,761,538

ELECTROMAGNETIC CONTROLS Filed Aug. 12, 1953 2 Sheets-Sheet 2 FIG 4motor.

United states Patent ELECTROMAGNETIC CONTROLS Ralph L. Jaeschke,Kenosha, Wis, assignor, by mesne assignments, to Eaton ManufacturingCompany, Cleveland, Ohio, a corporation of Ohio Application August 12,1953, Serial No. 373,704

3 Claims. (Cl. 192-21.5)

This invention relates to electromagnetic controls and more particularlyto speed-responsive and residual magnetism cancellation controls such asmay be used, for example, in excitation circuits of electric clutchesand the like on automotive vehicles.

Among the several objects of this invention are the provision ofspeed-responsive switch controls which are particularly useful inconnection with vehicle engines; the provision of controls of this typewhich are inexpensive in construction and reliable in operation; theprovision of such controls which may be conveniently adjusted; and theprovision of controls which cancel the residual magnetic effects inelectromagnetic couplings. Other objects and features will be in partapparent and in part pointed out hereinafter.

Briefly, the invention is directed to a speed-responsive switch controlcomprising a rectifier unit, an electrical relay having a coil and atleast one pair of electrical contacts and a condenser connected acrossthe relay coil. The relay coil and rectifier are series-connected acrossthe distributor circuit interrupter or contact breaker of an internalcombustion engine so that, when the engine speed exceeds a predeterminedvalue, the relay contacts are actuated. The invention is also directedto control apparatus for electromagnetic couplings such as brakes orclutches which provide a reverse current flow through an exciting coilof coupling during decoupled periods which cancels residual magneticeffects in the members of the coupling.

The invention accordingly comprises the constructions hereinafterdescribed, the scope of the invention being indicated in the followingclaims.

In the accompanying drawings, in which several of various possibleembodiments of the invention are illustrated,

Fig. 1 is a diagram showing a speed-responsive switch control of thepresent invention associated with the ignition system of a motorvehicle;

Fig. 2 is a graphic representation of the voltage across a circuitinterrupter plotted as a function of time;

Fig. 3 is a graphic representation of the relay voltage plotted as afunction of motor speed; and,

Fig. 4 is a circuit diagram of a second embodiment of the inventionconnected in an automotive vehicle clutchcontrol circuit and includingcontrol apparatus for cancellation of residual magnetic effects in theclutch.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawmgs.

The engine-speed-responsive switches in general use today are usuallycontrolled by centrifugal governors. Such switches are relativelyexpensive and are not conveniently adjustable. In accordance with thepresent invention, I have devised speed-responsive switch controls whichderive their actuating signal from pulses generated in the coil-ignitionsystem of an internal-combustion These controls are inexpensive,reliable and easily adjustable.

Patented Sept. 4, 1956 type conventionally employed in motor vehicles isin- I dicated by reference numeral 1. One terminal of a primary winding3 of a high-tension induction transformer 5 is connected through anignition switch 7 to battery 1. The other terminal of primary 3 isconnected to a circuit interrupter or contact-breaker 9 of a stand ardautomotive distributor 11. A condenser 13 of the type usually employedin distributors is connected across breaker 9. The electrical seriescircuit including battery 1, ignition switch 7, primary 3 and breaker 9is completed through the illustrated ground connections. A conventionalignition resistor may also be connected in series with this circuit, ifdesired. A secondary Winding 15 of transformer 5 is connected betweenground and a central terminal 17 of a head 19 of distributor 11. Otherterminals 21 are connected to spark plugs of an internal-combustionengine, one of which is illustrated at reference numeral 23. Thehigh-tension or secondary circuit includes secondary winding 15, adistributor brush 25, distributor terminals 17 and 21, plugs 23 and theground return. The lower terminal of winding 15 can be made electricallycommon to the lower terminal of primary 3 rather than being grounded,but is not shown, being a Well-known alternative. Brush 25 is mounted onone end of a distributor shaft 27 which also carries a cam 29 forintermittently opening the contacts of breaker 9. Shaft 27 is driven bythe internal-combustion engine, usually by the camshaft through a gearsuch as is indicated at reference numeral 31.

A series circuit, comprising rectifier unit 33 and a condenser 35, isconnected across the contacts of breaker 9. Coil A of a relay 37, havingcontacts A-1 and A-2, is connected in parallel with condenser 35.

Operation is as follows:

Upon closing the ignition switch 7, the primary circuit of transformer 5is completed and a direct current will flow through winding 3 andbreaker 9. When the internal-combustion engine is started, shaft 27 isrotated at the motor speed and will cause intermittent opening andclosing of breaker 9 in response to movement of cam 29. A signal voltageis thereby developed across the contacts of breaker 9, such as isexemplified in Fig. 2. The developed signal voltage, which during normaloperation may have an amplitude on the order of 60 volts at engineidling speed, consists of a series of substantially square-wave pulses.This signal is impressed across rectifier 33 and the R-C circuitcomprising the resistance of relay coil A and the capacitance ofcondenser 35. This signal is relatively constant in amplitude and has afrequency which is a function of engine speed. As the speed of theengine increases, the voltage impressed across relay coil A (due to theincreased frequency of the signal fed to this R-C circuit) increasessubstantially proportionately, as shown in Fig. 3.

The amplitude of the voltage across coil A is determined by severalfactors, including the amplitude and pulse frequency of the signal; thecapacitance of condenser 35; and the resistance of coil A. The contactsA-1 and A-2 of relay 37 will be actuated to a closed position when theamplitude of this voltage across coil A exceeds that at which relay 37is designed to be energized. Conversely, when the amplitude of thisvoltage across coil A falls below the value necessary to keep contactsA-1 and A-2 actuated, they will be deactuated.

Relay 37 may be selected from any of the semisensitive types of relaysknown to the art. It should have a coil with a relatively high D. C.resistance, so that the coil ignition circuit will not be adverselyaffected by the load thereof. Exemplary values for this coil are5,000-l0.,000 ohms and for condenser 35 are 0.1-1.0 mfd.

progressively .tional shift lever of a motor vehicle.

Rectifier '33, 'which is preferably a diode type rectifier,

prevents discharge of condenser during the time that the contacts ofbreaker 9 are closed.

The secondary circuit of transformer 5 functions in its usual capacity-to supply-timed high-tension pulsesto disributor 11 for sequentiallyenergizing the--respeetive p ue It can be seen, therefore, that theactuation of 'the relay contacts in response to engine speed can-beutilized in controlling various operationsin an automotive vehicleinresponse to engine speed. An exemplary embodiment of my control inclutch apparatus isillustrated in Fig. 4.

In Fig. 4, reference numeral '39 indicates afield coil, preferably of anelectromagnetic clutch of a type'having inherent self-modulatingcharacteristics adapted for nonslip or minimum slip operation aftermodulated engagement. The clutch comprises an armature M and a fieldmember F. Examples of clutches of this general type are disclosed in U.S. Patents 2,519,449, 2,525,571, 2,543,394 and 2,580,869. Patents2,519,449 and 2,543,394 show electromagnetic couplings includingrelatively rotary armature and field members with a magnetic gaptherebetween containing magnetizable fluid or flowable material.

Clutch field coil 39 is connected to battery 1 through contacts 8-1 and8-2 of a relay 41, a sequential-contact or caterpillar type modulatingcurrent controller 43, ignition switch 7, and a ground return. Thecurrent controller has a series of contacts 42 normally spaced from oneanother and adapted to be sequentially closed by movement of an actuator44 in the direction indicated to short-circuit resistor segments 40.Actuator 44 in turn is mechanically coupled to an accelerator 46 of themotor vehicle so that the controller 43 is actuated in thedirection'indicated as the accelerator is depressed against the bias ofspring 48. A circuit utilizing such a controller is described in moredetail in the copending U. S. application ofAndrew S. Gill, Jr., SerialNo. 280,086, filed April 2, 1952, now Patent No. 2,688,388, issuedSeptember 7, 1954.

The actuation of contacts B-1 and 3-2 is controlled by a coil B of relay41 which is connected to battery 1 by a circuit including ignitionswitch 7, a shift switch means 45, an acceleratorposition switch 47, anda ground return connection.

Shiftswitch means 45. is responsive to initiation and completion of amanual shifting operation of a conven- For example, it may. be a switchmechanism such as described-in the aforementioned copending applicationSerial No. 280,086. Switch 45. therefore, will be normally closed exceptfrom the time the movement 'ofthe switching lever is'initiated until thetime the switch lever is released,

Switch :47 is mechanically coupled to the motorvehicle accelerator pedal46 t'trough a suitable actuator 44, so

that Its contacts are closed only when accelerator 46 is depressed fromits idling position. A by-pass circuit is provided across controller 43consisting-of a'resistor R1, an auxiliary relay coil AA associated withrelay 37, contacts A1 and switch '45. Contacts A-Zare shunt-connectedacross switch 47. A pair of residual cancellation resistors R2 and R-3is connected to the opposite ends of clutch coil 59. These two resistorsR2.and R-3-and contacts 8-1 and 3-2 comprise control apparatus forcanceling residual magnetic effects in the coupling memlbersassociatedwith the excitingmeans or field coil 39.

The speed-responsive switch controlemployed in Fig. 4 to cooperate incontrolling the action-ofclutch'coil 3-9 is similar to that'describedinFig. l, exceptithat it includes the auxiliary winding AAandangadjustableresister 49 connected in series with rectifier 33 andrelay coil A.

Operation of the apparatus of Fig. 4 is as :follows: With the ignitionswitch 7 closedxandqthe motor vehicle shift lever in low-gear position(switch 45 being -closed), initial depression of the accelerator will'close switch 47 and complete the circuit to energize relay coil B frombattery 1. This action actuates contacts B-1 and B-2 to a closedcondition and completes the electrical circuit from battery 1 to clutchcoil 39 via controller 43 and contacts B-2 and B-1. Increased depressionof the accelerator will decrease the resistanceof controller 43 andthereby increase the current flow through clutch coil 39 to couple thedriving engine to the transmission. If. the transmission is of theautomatic type, the transmission will change gears automatically as thevehicle speedincreases. If the transmission is manually controlled (asis shown in the aforesaid copending U. S. application Serial No.280,086), then the gears are manually changed and the clutch coildeenergized during each shifting operation by the opening of shiftswitch 45. In either event, when the engine speed exceeds thepredetermined value necessary to energize relay 37, the contacts A-1,A-Z are actuated to a closed position. Contacts A-Z complete a holdingcircuit across switch 47 so that release of the accelerator at enginespeeds in excess of the predetermined value will not deenergize coil B(which would otherwise deenergize clutch coil 39). Contacts A-l closethe bypass circuit (including resistance R1, auxiliary winding AA andswitch 45) across the controller 43, which ensures that releasing theaccelerator at motor vehicle speeds in excess of the predetermined valuewill not decrease current flow through coil 39 below a point necessaryto retain adequate clutch coupling.

Current flow through auxiliary winding AA decreases the differential ofrelay 37. By differential, I mean ,the difference between the potentialacross relay 37 necessary to actuate its contacts (as the engine speedincreases) and the potential below which the actuated relay will becomedeactuated (as the engine speed decreases to a value below thepredetermined value). By employing such an auxiliary series winding andenergizing it to produce a field in opposition to that of coil A, thecontacts A-1 and A-2 ,willopen at substantially the same value ofvoltage (across coil A) as was initially necessary to close thecontacts. It will be noted that, if the accelerator is fully depressed(thus efiectively shunting out all the resistance ofcontroller 43), nocurrent will flow through'auxiliary winding AA. This is desirable undercertain conditions. And, in any event, the ditferentiating effect ofauxiliary WindingAA is primarily useful only when the engine speed isdecreased below its predetermined value. This isnot likely to be thecase when the accelerator is fully depressed. This auxiliary coil isonly energized during the period when the contacts A-1 and A2 areclosed. By use ofv this auxiliary winding, very inexpensive relays canbe used, rather than the high-costrelays which are designed to have alow differential. Upon the engine speed decreasing below thepredetermined value, contacts A-1 and A-2 will open. However, clutchcoil 39 will remain energized until switch .47 is opened by releasingthe accelerator, or until switch lever 45 is opened by movement of theswitch lever. When either of these switches is opened (at speeds belowthe predetermined value), the circuit to clutch 39 will ,be broken bythe opening of relay 41.

- Resistor49 functions to increase or decrease the sensitivity (i. e.,current flow through coil A) of relay 37 so that the predetermined valueof engine speed which will produce the voltage level needed toactuateA-l and A-2 may be varied conveniently. This adjustableresistance .may be physically located in the motor vehicle at a positionfrom which it may be readily manually adjusted. Also, the resistance ofresistor 49 may be responsive to the positioning of the accelerator 46by connecting the .arm of this resistor through any ,of a linkage to theac- :celerator as illustrated in Fig. 4. This arrangement would beparticularly :useful'in motor vehicles having automatic transmissionswhere variable .gear changes :are required, dependent upon engine speedand accelerator-positioning.

The point at which A1 and A-2 are actuated in such an instance would bea function of both the engine speed and accelerator position. In such acase actuation of the contacts of relay 37 is increasingly delayed withincreased accelerator displacement. Alternatively, instead of varyingthe sensitivity of relay 37 by resistor 49 (either manually or inresponse to accelerator position), the actuation point could be variedby providing multiple coils for relays 37 to add to or subtract from theefiFect of coil A. By the use of a conventional switching system, thesensitivity of relay 37 could be changed so that in one positioncontacts A-1 and A2 would be actuated at a first predetermined value ofengine speed (with a first combination of the multiple coils) and in asecond switch position the contacts would be actuated at a secondpredetermined value of engine speed (with a second combination of themultiple coils).

In order to ensure very rapid decoupling and cancellation of residualmagnetism of the electromagnetic clutch, control apparatus includingresistors R-2 and R-3 is provided. It will be noted that when contactsB-1 and B-2 open, a reversed current is caused to flow from battery 1via resistor R-3 through clutch coil 39 and resistor R-2. This currentflow is sufiicient to cancel the residual magnetism or the clutch, butis not sufi'icient to reengage or couple the clutch members. The valuesof these resistors R-2 and R3 are relatively high (as compared to theresistance of coil 39) so that the energy consumed by them (whencontacts B-1 and B-2 are closed) is only a few percent (e. g., 2%l0%) ofthe energy supplied to coil 39.

These resistors may be omitted if the remanence of the clutch members isof only slight consequence or if the speed of clutch release issufiiciently rapid without them. Rapid decoupling also can be obtainedby providing reverse current flow through coil 39 for only an instantafter contacts B-1 and B-2 are opened. The details of such arrangementsare described more fully in the aforementioned U. S. application SerialNo. 280,086.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. Control apparatus for an electromagnetic coupling having relativelyrotary armature and field members with a magnetic gap therebetweencontaining magnetic fluid, said field member carrying exciting meanshaving first and second input terminals adapted when electricallyenergized to couple said members, and a source of electric currenthaving first and second oppositely polarized terminals adapted toenergize said exciting means; said control apparatus comprising a firstpair of contacts adapted to interconnect said first input terminal andsaid first polarized terminal, a second pair of contacts adapted tointerconnect the second input terminal and the second polarizedterminal, a first resistor connected between said first input terminaland said second polarized terminal, and a second resistor connectedbetween said second input terminal and said first polarized terminal,whereby on actuation of both pairs of said contacts current is caused toflow in one direction through said exciting means to couple said membersand on deactuation of both pairs of said contacts current is caused toflow in a reverse direction through said exciting means.

2. Control apparatus as set forth in claim 1 wherein the resistance ofeach of said resistors is substantially greater than the resistance ofsaid exciting means, whereby the current caused to flow through saidexciting means when said pairs of contacts are actuated is substantiallygreater than the value of reverse excitation current.

3. Control apparatus as set forth in claim 1 wherein the resistance ofsaid exciting means is not greater than approximately 10% of theresistance of each of said resistors whereby the reverse current causedto flow through said exciting means is substantially less than the valueof excitation current and cancels residual magnetism of said members.

References Cited in the file of this patent UNITED STATES PATENTS799,720 Cutler Sept. 19, 1905 2,364,751 Place Dec. 12, 1944 2,367,413Lucarelle Jan. 16, 1945 2,381,250 Baumann Aug. 7, 1945 2,435,280 JaegerFeb. 3, 1948 2,637,416 Guernsey May 5, 1953 2,642,484 Price June 16,1953 OTHER REFERENCES Publication: The Magnetic Fluid Clutch, Paper No.48238AIEE Transactions; December 13, 1948, vol. 67, 1948.

